One of the things that we've worked on for VS 2005 is something we call Data Designer EXtensibility (DDEX). It allows various database providers to hook into VS more cleanly. Jim Glass has a post on the topic on his blog - which was co-written by Milind and Stephen from my team.
For those who are interested, Milind has written a few other posts on the subject:
The documentation on this should be out with the VSIP docs for Beta 2.